There have been conventionally known the sliding devices of a completely enclosed type that is adapted for use in the semiconductor manufacturing machines, machine tools, assembly machines, testing machines, and so on, which are needed to operate in the clean rooms. A prior sliding device of the type stated earlier is disclosed in, for example Japanese Patent Laid-Open No. 2003-222129, in which sealing members of foam rubber fit in seal holders that are each made up of a seal support portion and a cover portion integral with the seal support portion, the seal holders being attached at their cover portions onto widthwise opposite sides of a guide rail. The sealing member is made of porous material rich in flexibility and restoration to its original state. The sealing members fit into recesses in the seal support portions in opposition to each other to come into abutment against one another, thereby close a clearance between the seal support portions of the seal holders. The slider has a table extending through between the opposite sealing members to the outside to carry any object thereon. As the slider travels in the lengthwise direction of the guide rail, the table moves with getting deforming the sealing members, but keeping close sliding-contact with the sealing members. With the sliding device constructed as stated earlier, the clearance between the opposite seal holders is kept closed constantly while the slider travels. Thus, the sliding device is better for clean environment as well as improved in durability and dust-proofing property, even with slim in construction.
A linear motion actuator causing little dust is disclosed in, for example Japanese Patent Laid-Open No. H8-290384, in which a driving motor is arranged side by side with a linear motion guide unit encased within an enclosure. The driving motor is also enclosed in a container reduced in pressure below the atmosphere to keep any airborne dust against going away into the atmosphere. A seal belt is jointed at one end thereof with any one end of a carriage and at another end thereof with another end of the carriage to be brought in endless form. The seal belt fits over pulleys at forward and aft ends inside the enclosure in a way closing a lengthwise slit. There are provided tubes made opened near axially opposite ends inside the enclosure to bleed the enclosure of air. The bleeder tubes serve effective function to purge air that is raised in pressure at the axially opposite ends as the carriage reciprocates with high velocity, thereby keeping any dust against going away out of the atmosphere.
A movable table unit is disclosed in, for example Japanese Patent Laid-Open No. H9-144830, in which a driving source lies side by side with a lead screw. The prior movable table unit is composed of a lead screw to connect a driving source to a table carried on a guide rail, and a nut fastened to the table. This prior table unit does away with a support frame to shrink the unit down. With the movable table unit recited above, the lead screw is born against a support plate attached to any one end of the guide rail while the driving source is mounted on the support plate with using a bracket. The table unit is secured to any other object along the guide rail.
Nevertheless, the sliding device as first recited earlier has a constructional issue that as the driving motor is installed in tandem with the guide rail in a relation an output shaft of the motor lies generally on the extension of an axial line of a lead screw, the sliding device is too large in the overall length inclusive of both the lead screw and the driving motor to use it in the appliance constrained in lengthwise dimension. Making the sliding device shorten in overall axial length, thus, was a major challenge for this sort of sliding unit.
With the linear motion actuator second recited earlier in which the lengthwise clearance slit into the enclosure is closed with the seal belt made in the endless form fit over four pulleys, it was needed to collect airborne dust inside the enclosure through some air bleeder tubes and further enclose entirely the driving motor with any other covering material. With this type of linear motion actuator constructed as stated earlier, any airtight packing has to be applied at the junction of the enclosure with the motor covering. Thus, problems faced in the linear motion actuator recited earlier are that the actuator unit by itself has to be made large scale in construction and further that the actuator unit is tougher for installation in a posture easy to operate it.
With the movable table unit third recited earlier, top and side covers are disposed between the bracket and the support plate while the driving source is shielded together with the coupler by using a covering and also a drive train is enclosed with another covering. The lead screw extends outside the covering and ends in a manipulator. Considering the construction as stated just above, this prior table unit has no technical concept of the provision of airtight construction and therefore is envisaged usage in the clean environment.